We got dinner there last night, and we have eaten at both the old location and the new. Last night got the curry puffs, panang curry, and the tom yum soup. We didn't notice a huge decrease in the heat but at the same time I have previously ordered the floating market noodle soup and couldn't eat it because it was too hot (I am more sensitive to severe heat so I generally stay away from the 3 pepper dishes, two is my limit!) but the tom yum and curry were at a heat levels I remembered.
Possibly they are reducing the heat amount of the FMNS because they are serving so many more people. When I went to pick-up our food the place was packed, for a Tuesday night I think that is fantastic. But with more people coming in they may be tweaking the heat amount to accomodate more patrons who can't stand such high levels of heat. Just a thought, I know that defeats the whole purpose of having this really traditional Thai food but they can't have lots of people sending food back and earn a profit.